Stem cell scientists in the United Kingdom are reporting today a gene discovery that suggests a way to take adult cells back to an embryonic state -- a discovery that could help treat diseases without relying on controversial human embryonic stem cells or cloning.

The ultimate goal would be to use a patient's own cells as the starting material for a new kind of regenerative medicine. But scientists insisted that they will need to use embryonic cells for the foreseeable future to perfect the new techniques.

A team led by Austin Smith at the University of Edinburgh's Institute for Stem Cell Research published the latest results online in the journal Nature. The study used mouse cells to investigate the critical role of one gene in the process by which a stem cell, when fused to a more specialized adult stem cell found in the brain, reprograms the brain cell into a primitive state.

Reprogramming adult cells to give them this core trait of an embryonic stem cell could dramatically reshape both the science and politics of the stem cell field, which is fraught with controversy because the embryonic stem cells require the destruction of human embryos.

For example, reprogramming could make it possible to generate from a patient's skin cells customized cells of other types that had been destroyed by spinal cord injury or diseases such as Parkinson's or diabetes. Self-renewing lines of human cells also might be used to study how genetic diseases come about and how treatments could affect the disease process.

Smith said in an interview that reprogramming could take at least another year of experimental work to be well understood. Yet it no longer seems the deep mystery it was before the latest studies, which reveal the role of a gene known as "nanog."

Smith called nanog "the key gene in the process."

"We thought this was something that would take us a very long time to work out, but now this changes from being a black box to something we can work to understand," he said.

Nanog appears to be the most important among a handful of reprogramming genes, but there are also some chemical factors that kick in as a cell goes through its full life cycle. "Reprogramming is a very complicated business," said Vincenzo Pirrotta at Rutgers University.

Dr. Robert Blelloch, a stem cell scientist at UCSF who participated with the British researchers on previous experiments, said unknown factors in brain cells also appear to be playing a role, making it easier to endow neurons with the transformative properties collectively known as "stemness."

Blelloch is one of the researchers now aiming to apply the results of the mouse studies to human cells to produce a true reprogramming tool kit for regenerative medicine. The ultimate goal, he said, is "to bring it all together, and in the culture dish convert a differentiated cell back to an embryonic cell."

"I don't think it's going to be just three or four genes," Blelloch added, "but three or four genes combined with the cell cycle and something else we still need to understand."

Other scientists are pursuing similar goals through stem cell cloning experiments, in which a person's DNA is inserted into a human egg whose nucleus has been removed. Nobody knows which of the avenues might be first to yield success.

Scientists insisted it will take human embryonic stem cells -- and the destruction of some embryos -- in virtually any scenario despite the long-term promise of alternative strategies.

"We will need embryonic stem cells to get there," Pirrotta said. "Every embryonic stem cell line is not the same, and they change over time. So we will need a diversity of lines to test, and we will need to be producing new lines over time because the old lines basically wear out."

Reprogramming adult cells to become stem cells

One of the more promising ideas in regenerative medicine is to reprogram adult cells so they become like stem cells - potentially a source of replacement parts for diseased organs. This would bypass the need to use the controversial human embryonic stem cells. The latest experiments, reported today in the journal Nature, highlight the key role of a gene known as nanog:

The discovery of a critical gene

1 Stem cell is fused with a special brain cell of a mouse, producing a hybid cell.

2 Fusing these cells produced a cell that took on characteristics of a more primitive state, with traits of an embryonic stem cell.

3 This led scientists to discover that nanog played a critical role in the process.

Differentiation of cells

4 The reprogramming of adult cells using nanog could make it possible for scientists to generate cells that specialize and develop into every type of cell in the body.

Endoderm

Pancreas

Stomach

Lungs

Ectoderm

Hair

Eyes

Nerves

Mesoderm

Heart

Bones

Muscle

Sources: Nature, University of Edinburgh, Institute for Stem Cell Research